diff --git a/app/Main.hs b/app/Main.hs
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -8,7 +8,7 @@
                                                        minimumPgVersion,
                                                        prettyVersion,
                                                        readOptions)
-import           PostgREST.Error                      (prettyUsageError)
+import           PostgREST.Error                      (encodeError)
 import           PostgREST.OpenAPI                    (isMalformedProxyUri)
 import           PostgREST.DbStructure
 import           PostgREST.App                        (postgrest)
@@ -80,7 +80,7 @@
     getDbStructure (toS $ configSchema conf)
 
   forM_ (lefts [result]) $ \e -> do
-    hPutStrLn stderr (prettyUsageError e)
+    hPutStrLn stderr (toS $ encodeError e)
     exitFailure
 
   refDbStructure <- newIORef $ either (panic . show) id result
diff --git a/postgrest-ws.cabal b/postgrest-ws.cabal
--- a/postgrest-ws.cabal
+++ b/postgrest-ws.cabal
@@ -1,5 +1,5 @@
 name:                postgrest-ws
-version:             0.1.0.2
+version:             0.1.0.3
 synopsis:            PostgREST extension to map LISTEN/NOTIFY messages to Websockets
 description:         Please see README.md
 homepage:            https://github.com/diogob/postgrest-ws#readme
@@ -57,7 +57,7 @@
                      , warp >= 3.2 && < 4
                      , unix >= 2.7 && < 3
                      , jwt >= 0.7 && < 1
-                     , postgrest
+                     , postgrest >= 0.4.1.0
                      , postgrest-ws
                      , postgresql-libpq >= 0.9 && < 1.0
                      , protolude >= 0.1.6 && < 0.2
diff --git a/src/PostgRESTWS/Broadcast.hs b/src/PostgRESTWS/Broadcast.hs
--- a/src/PostgRESTWS/Broadcast.hs
+++ b/src/PostgRESTWS/Broadcast.hs
@@ -1,3 +1,13 @@
+{-|
+Module      : PostgRESTWS.Auth
+Description : PostgRESTWS functions to broadcast messages to several listening clients
+
+This module provides a type called Multiplexer.
+The multiplexer contains a map of channels and a producer thread.
+
+This module avoids any database implementation details, it is used by HasqlBroadcast where
+the database logic is combined.
+-}
 module PostgRESTWS.Broadcast ( Multiplexer (src)
                              , Message (..)
                              , SourceCommands (..)
@@ -7,7 +17,7 @@
                              , relayMessagesForever
                              , openChannelProducer
                              , closeChannelProducer
-                             -- reexports
+                             -- * Re-exports
                              , readTQueue
                              , writeTQueue
                              , readTChan
@@ -34,15 +44,19 @@
                        , close :: STM ()
                        }
 
+-- | Open a multiplexer's channel
 openChannelProducer :: Multiplexer -> ByteString -> STM ()
 openChannelProducer multi ch = writeTQueue (commands multi) (Open ch)
 
+-- | Close a multiplexer's channel
 closeChannelProducer ::  Multiplexer -> ByteString -> STM ()
 closeChannelProducer multi chan = writeTQueue (commands multi) (Close chan)
 
+-- | Opens a thread that relays messages from the producer thread to the channels forever
 relayMessagesForever :: Multiplexer -> IO ThreadId
 relayMessagesForever =  forkIO . forever . relayMessages
 
+-- | Reads the messages from the producer and relays them to the active listeners in their respective channels.
 relayMessages :: Multiplexer -> IO ()
 relayMessages multi =
   atomically $ do
@@ -72,23 +86,31 @@
     openChannelProducer multi chan
     return newChannel
 
+{- |  Adds a listener to a certain multiplexer's channel.
+      The listener must be a function that takes a 'TChan Message' and perform any IO action.
+      All listeners run in their own thread.
+      The first listener will open the channel, when a listener dies it will check if there acquire
+      any others and close the channel when that's the case.
+-}
 onMessage :: Multiplexer -> ByteString -> (TChan Message -> IO()) -> IO ()
 onMessage multi chan action = do
-  listener <- atomically $ do
-    mC <- M.lookup chan (channels multi)
-    c <- case mC of
-              Nothing -> openChannel multi chan
-              Just ch -> return ch
-    M.delete chan (channels multi)
-    let newChannel = Channel{ broadcast = broadcast c, listeners = listeners c + 1, close = close c}
-    M.insert newChannel chan (channels multi)
-    dupTChan $ broadcast newChannel
-  void $ forkFinally (action listener) (\_ -> atomically $ do
-    mC <- M.lookup chan (channels multi)
-    let c = fromMaybe (panic $ "trying to remove listener from non existing channel: " <> toS chan) mC
-    M.delete chan (channels multi)
-    when (listeners c - 1 == 0) $ closeChannelProducer multi chan
-    when (listeners c - 1 > 0) $ do
-      let newChannel = Channel{ broadcast = broadcast c, listeners = listeners c - 1, close = close c}
+  listener <- atomically $ openChannelWhenNotFound >>= addListener
+  void $ forkFinally (action listener) disposeListener
+  where
+    disposeListener _ = atomically $ do
+      mC <- M.lookup chan (channels multi)
+      let c = fromMaybe (panic $ "trying to remove listener from non existing channel: " <> toS chan) mC
+      M.delete chan (channels multi)
+      if listeners c - 1 > 0
+        then M.insert Channel{ broadcast = broadcast c, listeners = listeners c - 1, close = close c} chan (channels multi)
+        else closeChannelProducer multi chan
+    openChannelWhenNotFound =
+      M.lookup chan (channels multi) >>= \mC ->
+      case mC of
+            Nothing -> openChannel multi chan
+            Just ch -> return ch
+    addListener ch = do
+      M.delete chan (channels multi)
+      let newChannel = Channel{ broadcast = broadcast ch, listeners = listeners ch + 1, close = close ch}
       M.insert newChannel chan (channels multi)
-    )
+      dupTChan $ broadcast newChannel